Window regulator mechanism

ABSTRACT

A window regulator mechanism adapted to lower or raise a window panel into and out of a window well between vehicle body panels, the window panel being vertically divided into separately movable ventilation and visibility sections. With the window panel in raised condition, the mechanism first may be actuated to lower the ventilation section into the window well to provide a ventilation exhaust opening in the vehicle body and then, if desired, further actuated to lower the visibility section into the window well. From a lowered condition, the sequence of movements to raise the panel sections is reversed. Movement of the panel sections is controlled by a series or train of links effective to transmit movement of a gear sector to the window regulator arms coupled to the respective ventilation and visibility sections. Each train of links is controlled by a cam follower movable in a cam slot in a respective cam plate. The cam slots are programmed to permit or restrain vertical movement of the panel sections in a desired sequence in window panel lowering or raising directions.

United States Patent [191 Mistopoulos, Jr.

.[ WINDOW REGULATOR MECHANISM Chris Mistopoulos, Jr., Detroit, Mich.

[73] Assignee: Ford Motor Company, Dearborn,

Mich.

[22] Filed: Feb. 12, 1973 [21] Appl. No.: 331,929

[75] Inventor:

[52] US. Cl 49/103, 49/227, 49/351 [51] Int. Cl E05f 5/12 [58] Field of Search 49/103, 227, 349, 350

[56] References Cited UNITED STATES PATENTS 2,955,817 10/1968 Campbell et al 49/227 X 3,659,381 5/1972 Frey et al 3,670,454 6/1972 Gebhard et al. 3,733,748 5/1973 3,745,703 7/1973 Francis et al. 49/351 X Primary Examiner-Kenneth Downey Attorney, Agent, or Firm-Keith L. Zerschling and John J. Roethel Jan. 29, 1974 [57] ABSTRACT A window regulator mechanism adapted to lower or raise a window panel into and out of a window well between vehicle body panels, the window pane] being vertically divided into separately movable ventilation and visibility sections. With the window panel in raised condition, the mechanism first may be actuated to lower the ventilation section into the window well to provide a ventilation exhaust opening in the vehicle body and then, if desired, further actuated to lower the visibility section into the window well. From a lowered condition, the sequence of movements to raise the panel sections is reversed.

Movement of the panel sections is controlled by av series or train of links effective to transmit movement of a gear sector to the window regulator arms coupled to the respective ventilation and visibility sections. Each train of links is controlled by a cam follower movable in a cam slot in a respective cam plate. The cam slots are programmed to permit or restrain vertical movement of the panel sections in a desiredsequence in window pane] lowering or raising directions.

16 Claims, 4 Drawing Figures PATENTEDJAHZQ I974 3 788005 sum 1 or 3 1 WINDOW REGULATOR MECHANISM BACKGROUND OF THE INVENTION US. Pat. No. 3,650,381 issued to Stewart M. Frey et al. on May 2, 1972 and US. Pat. No. 3,670,454 issued to Harold C. Gebhard on June 20, 1972, each disclose variations of window regulator mechanisms for raising and lowering in a window opening in a vehicle body structure a window panel vertically divided into a ventilation section and a visibility section. A single window regulator mechanism is utilized to raise and lower each panel in controlled sequence. The mechanisms are somewhat complicated in that unique and complex latch mechanisms are provided to hold the large visibility sections against movement in any position of the ventilation section other than when the latter is fully lowered.

It is an object of the present invention to provide a single window regulator mechanism for raising and lowering the visibility and ventilation sections in which no complex latch mechanisms are used and in which the sequence of movements and the restraint of the visibility section against movement in any position of the ventilation section other than in fully lowered position of the latter is achieved through a linkage system controlled by cam followers movable in suitably programmed cam slots in cam plates.

SUMMARY OF THE INVENTION This invention relates to a window regulator mechanism adapted to lower or raise a window panel into or out of a window well between vehicle body panels, the window panel being vertically divided into separately movable ventilation and visibility sections. The window regulator mechanism comprises a mounting plate secured to one of the body panels. A gear sector is pivotally mounted on a pivot shaft journalled in the mounting plate. First and second regulator arms each swingable at one of its ends about a common pivot axis also are supported on the mounting plate. The other ends of the first and second regulator arms are coupled, respectively, to the ventilation section and the visibility section of the window panel.

A drag link is pivotally connected to the gear sector for swinging movement in response to movement of the gear sector. The drag link is coupled to the first and second regulator arms by a first and a second drive link. A first and a second cam plate are positioned on the body panel to which the mounting plate is secured in predetermined relationship to the latter. Each cam plate has a cam slot therein and each of the drive links carries a cam follower engaged with a cam slot in a respective cam plate. The cam slots are programmed so that movement of a follower therein controls the trans mittal of movement of the gear sector through the drag link and drive links to the respective regulator arms.

Upon actuation of the window regulator mechanism, a predetermined degree of gear sector rotation in window panel lowering direction causes the first link, under control of its cam follower as the latter moves through a first section of the cam slot in the respective cam plate, to drive the first regulator arm and thereby the ventilation section to a predetermined position in the window well. Simultaneously, the cam follower on the second drive link moves along a first section of the cam slot in the respective or second cam plate without causing the second drive link to drive the second regulator arm and thereby the visibility section in window panel lowering direction. During this phase the visibility section of the window panel is restrained by the second drive link against any attempt to force the panel section in lowering direction by the direction application of downward force to the panel section.

Upon further gear sector rotation, the second drive link, under control of its cam follower as the latter moves along a second section of the cam slot in the second cam plate, is caused to drive the second regulator arm and thereby the visibility section in window panel lowering direction. In this phase of the movement, the cam follower on the first drive link moves along a second section of the cam slot in the first cam plate but does not cause the first drive link to further drive the first regulator arm and thereby the ventilation section in any further window panel lowering direction.

The gear sector is rotated through the conventional drive pinion means as found in conventional window regulator mechanisms.

DESCRIPTION OF THE DRAWINGS Other objects, advantages and features of the present invention will become more apparent as the description proceeds, reference being had to theaccompanying drawings wherein:

FIG. I is a' perspective view of a vehicle body structure, such as a vehicle door, having a sectional window panel mounted therein adapted to be raised and lowered by a window regulator mechanism embodying the present invention;

FIG. 2 is a side elevational view of the window regulator mechanism illustrating the parts thereof in window panel raised position;

FIG. 3 is a view in part similar to FIG. 2 illustrating the parts thereof in a relationship in which the ventilation section of the window panel has been lowered and the visibility section is ready to begin its downward movement;

FIG. 4 is a view in part similar to FIG. 2 illustrating the parts of the window regulator mechanism when both the ventilation and visibility sections are in their lowermost positions within the vehicle body structure.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, there is illustrated in dot and dash outline a portion of a vehicle body structure, such as a door generally designated 11. The door has inner and outer panels 12 and 13, respectively, defining a window well. Between and on the panels 12 and 13 the various mechanical hardware items such as a door latch mechanism (not shown), a window guide assembly 14, a door glass run and bracket assembly 15, and a window regulator mechanism, generally deisgnated l6 and embodying the present invention, are mounted.

The window panel, generally designated 17, is vertically divided into two separately movable sections, a small front ventilation section 18 and a much larger main or visibility section 19. As in a conventional vehicle installation, the window panel 16 is adapted to be raised and lowered relative to the window well defined by the inner and outer panels 12-13 of the door structure 11. In accordance with the present invention, the window regulator mechanism 16 is constructed and arranged to raise and lower the window panel sections 18 and 19 in sequential movements, as will be more fully explained.

The window regulator mechanism 16 comprises a horizontally elongated base or mounting plate 2] adapted to be mounted as by bolts 22 to the inner door panel 12. A gear sector 23 is rotatably journalled on a pivot shaft 24 positioned at one end of the mounting plate, the gear sector 23 being freely rotatable on the shaft. The gear sector 23 is illustrated as being drivable in window raising or lowering direction by a conventional hand crank window regulator drive pinion and clutch assembly 25.

A pair of window regulator arms 26 and 27 are each pivotally mounted at one of its ends 28 and 29, respectively, on the regulator mounting plate 21. The first arm 26 is freely swingable about the gear sector pivot shaft 24 and the second arm 27 is keyed to the pivot shaft 24 for rotation therewith, for a purpose to be explained.

The free end 31 and 32 of each arm 26 and 27 carries a roller 33. The roller 33 on the end 31 of arm 26 rides in guide channel member 34 carried on a bracket 35 attached to the lower edge of the ventilation section 18 of the window panel 17. The roller 33 mounted on the free end of the arm 27 is engaged with and travels in a channel member 36 carried on a bracket 37 that is secured to the lower edge of the visibility panel section 19.

The bracket 37 is a part of the door glass run and bracket assembly which guides the rear portion of the window panel 17 as it is raised and lowered between the inner and outer body or door panels 12 and 13. The details of construction of the door glass run and bracket assembly form no part of the present invention.

The front portion of the window panel section 19 has a bracket 38 attached thereto which carries rollers 39 that engage the window guide assembly 14. The ventilation section 18 is also guided in its up and down movements relative to the visibility section 19 by a sealing channel 41 secured to the front edge of the visibility section 19.

Rotary movement of the gear sector 23 by the drive pinion assembly 25 is transmitted to the regulator arms 26 and 27 through a series or train of links including a drag link 42. The drag link 42 is a delta-shaped member having one corner 43 pivotally connected at 44 to the gear sector 23. An extension 45 of a second corner 46 of the drag link 42 is pivotally connected at 47 to one end 48 of an elongated angularly-shaped first drive link 49. This first drive link 49 is coupled at its other end 51 by a pin 52 to the first or ventilation section regulator arm 26, the pin being slidable in a longitudinal slot 53 in the arm 26 for a purpose to be explained.

The third corner 54 of the drag link 42 is pivotally connected at 55 to one end of a drive link 56 which extends to and is pivotally connected at 57 to the second or visibility section regulator arm 27.

Movements of the drive links 49 and 56 are controlled by cam plates 58 and 59, respectively. Cam plate 58 is located beneath the ventilation section 18 and comprises a plate member having one end 61 pivotally supported on the gear sector pivot shaft 24. At

the end 62 of the cam plate a suitable mounting bolt 63 is provided for holding the cam plate to the inner door panel 12. The pivotal mounting of the cam plate 58 provides for vertical adjustment of the cam plate before the bolt is tightened.

The cam plate 59 similarly is pivotally supported at one end 64 on the gear sector pivot shaft 24 and has provisions for mounting bolts 65. This cam plate 59 thus may also be adjusted about the pivot shaft 24.

The cam plate 58 has a cam slot 66 therein which, as best seen in FIG. 2, has an angularly downwardly inclined straight section 67 and a less angularly inclined terminal section 68. The cam slot 66 is traversed by a cam follower 69 carried on the pivot pin 52 connecting the first drive link 49 to the first regulator arm 26.

The cam plate 59 has a cam slot 71 consisting of an upper short arcuate section 72 and an elongated arcuate section 73 both of which extend in a generally downwardly direction. This cam slot 71 is traversed by a cam follower 74 carried on the pivot pin 55 connecting the drive link 56 to the drag link 42.

The weight of the visibility section 19 on the arm 27 is counterbalanced by a spiral spring 75. The spring 75 is coupled to the gear sector pivot shaft 24 to which the arm 27 is keyed and to the regulator mounting plate 21 in a conventional manner.

OPERATION Referring now to FIGS. 1 and 2, the window panel 17 is shown in a raised position relative to the window well in the vehicle body or door structure 11. That is, both the ventilation section 18 and the visibility section 19 are in their raised position and the related drive arms 26-27 are in corresponding raised positions.

lf it is now desired to provide exhaust ventilation of the vehicle passenger compartment by lowering the ventilation section 18, this can be accomplished by rotating the drive pinion assembly 25 in a counterclockwise direction, as viewed in the drawings, to drive the gear sector 23 in a clockwise direction. Upon the gear sector 23 being so rotated, the drag link 42 is bodily shifted angularly downwardly as it swings about its pivotal connection 44 with the gear sector 23. Movement of the drag link 42 is transmitted to the drive links 49 and 56. As described, each drive link is operatively associated with a cam plate which influences the translation of movement of the drive link to the respective regulator arm to which it is coupled.

For example, as the drag link 42 is bodily pulled angularly downwardly in a path curving beneath the gear sector shaft 23 it imparts an angularly downward movement to the drive link 49 coupled to the ventilation section window regulator arm 26 causing the latter to swing downwardly in a counterclockwise direction about the pivot shaft 24. The movement of the lower end of the drive link 49 is under control of the cam follower 69 as the latter traverses the straight section 67 of the cam slot 66 in the cam plate 58. The longitudinal extending slot 53 in the regulator arm 26 permits the cam follower 69 to move radially outwardly of the pivot axis 24 as the arm swings downwardly. Downward movement of the arm 26 continues until the cam follower reaches the juncture between the cam slot sections 67-68 at which time the lower end of the drive link 49 is guided outwardly and loses its ability to drive the arm 26 any further in a downward direction. Accordingly, the downward movement of the ventilation section 18 is completed and this is timed to occur with the upper edge of the ventilation section reaching a position beneath the upper edge of the vehicle window well.

During the time interval that the ventilation section 18 is moving downward, there is no corresponding movement of the visibility section. Although the drive link 56 coupled to the regulator arm 27 is being swung in a clockwise direction about its pivotal connection 57 to the arm 27, under the control of the follower 74 moving in the arcuate portion 72 of the cam slot 71, it is unable to impart any downward force to the arm 27. In effect, the link 56 acts as a prop or brace resisting downward movement of the arm 27. Thus, any attempt to force or jimmy the visibility section open is resisted, which is a desirable condition.

The follower 74 reaches the lower end of the arcuate section 72 of the cam slot 71 at about the same time the ventilation section 18 reaches its predetermined lowered position. As the follower 74 enters the arcuate section 73 of the cam slot 71, the visibility section is then permitted to move downwardly. This condition is illustrated in FIG. 3 where the follower 69 on the end of drive link 49 is shown at the end of slot section 67 in cam slot 66 and the follower 74 on the end of drive link 56 is shown at the lower end of arcuate section 72 of the cam slot 71. The ventilation section regulator arm 26 extends in a substantially horizontal direction and the visibility section regulator arm extends upwardly in its original position.

As rotation of the gear sector 23 continues so that the parts of the mechanism are moved from their FIG. 2 relationship toward the FIG. 3 relationship, the action is transferred to the visibility section 19. The pivot point 55, the connection of the drag link 42 to the drive link 56, is pulled downwardly as the cam follower 74 traverses the arcuate section 73 of the cam slot 71. The drag link 42 through the drive link 56 thus drags the regulator arm 27 and the visibility section 19 down against the increasing resistance of the counterbalance spring 75.

The drive link 49 cam follower 69 merely moves radially outwardly in slots 53 and 68 as the visibility section 19 is moved downwardly. There may be a slight incremental movement of the regulator arm 26 in a downward direction, due to the angle of the slot section 68, but for all practical purposes the opening of the ventilation section has been completed.

The sequence of movements is reversed upon the gear sector being rotated in a counterclockwise direction.

Downward movement of the window panel and its respective sections 18 and 19 may be interrupted at any time so that the ventilation section 18 may be partially opened or fully opened and the visibility section, after the ventilation section has been fully opened, may also be placedin a partially or fully opened condition. Conversely, during raising movement of the panel 17, the operation may be interrupted at any time so that the visibility section 19 may be partially or fully closed and subsequently, after the visibility section 19 is fully closed, the ventilation section 18 may be moved to a partially opened or fully closed position.

It is to be understood that this invention is not limited to the exact construction illustrated and described above, but that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. A window regulator mechanism adapted to lower or raise a window panel into or out of a window well between vehicle body panels,

the window panel being vertically divided into separately movable ventilation and visibility sections, the window regulator mechanism comprising:

a mounting plate secured to one of the body panels,

a gear sector rotatably mounted on a pivot shaft journalled in the mounting plate,

a first and a second regulator arm each swingable at one of its ends about a common pivot axis on the mounting plate,

the other ends of the first and second regulator arms being coupled, respectively, to the ventilation sec tion and the visibility section,

a drag link pivotally connected to the gear sector for swinging movement in response to movement of the gear sector,

a first and a second drive link each coupled at one of its ends to the drag link and at its other end to the first and second regulator arms, respectively,

a first and a second cam plate positioned on the one body panel in predetermined relationship to the mounting plate,

each cam plate having a cam slot therein,

a cam follower carried on each of the drive links engaged with a cam slot in a respective cam plate, the cam slots being programmed so that movement of a follower therein controls the transmittal of movement of the gear sector through the drag link and drive links to the respective regulator arms,'

a predetermined degree of gear sector rotation in window panel lowering direction causing the first drive link, under control of its cam follower as the latter moves through a first section of the cam slot in the first cam plate, to drive the first regulator arm and thereby the ventilation section to a predetermined position in the window well as the cam follower on the second drive link moves along a first section of the cam slot in the second cam plate in which the second drive link is inoperative to drive the second regulator arm and thereby the visibility section in window panel lowering direction,

and further gear sector rotation causing the second drive link, under control of its cam follower as the latter moves along a second section of the cam slot in the second cam plate, to drive the second regulator arm and thereby the visibility section in window panel lowering direction as the cam follower on the first drive link moves along a second section I of the cam slot in the first cam plate without causing the first drive link to further drive the first regulator arm and thereby the ventilation section in window panel lowering direction,

and drive pinion means for rotating the gear sector about its pivot axis.

2. A window regulator mechanism according to claim 1, in which: 1

. 7 3. A window regulator mechanism according to claim 2, in which:

the second drive link during movement relative to the first section of its related cam slot restrains downward movement of the visibility section upon the direct application of downward force to the latter. 4. A window regulator mechanism according to claim 3, in which:

the drag link is pivotally connected directly to the gear sector. 5. A window regulator mechanism according to claim 4, in which:

the second regulator arm is fixed to the pivot shaft to cause the latter to rotate in the mounting plate,

and counterbalance spring means coupled to the pivot shaft and mounting plate counterbalances the weight of the visibility section on the second regulator arm. 6. A window regulator mechanism according to claim 5, in which:

the first cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate when fastened to the body panel. 7. A window regulator mechanism according to claim 6, in which:

the second cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate. 8. A window regulator mechanism according to claim 1, in which:

the drag link is pivotally connected directly to the gear sector. 9. A window regulator mechanism according to claim 8, in which:

the second regulator arm is fixed to the pivot shaft to cause the latter to rotate in the mounting plate,

and counterbalance spring means coupled to the pivot shaft and mounting plate counterbalances the weight of the visibility section on the second regulator arm.

10. A window regulator mechanism according to claim 9, in which:

the first cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate when fastened to the body panel. 11. A window regulator mechanism according to claim 10, in which:

the second cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate. 12. A window regulator mechanism according to claim 1, in which:

the second regulator arm is fixed to the pivot shaft to cause the latter to rotate in the mounting plate,

and counterbalance spring means coupled to the pivot shaft and mounting plate counterbalances the weight of the visibility section on the second regulator arm. 13. A window regulator mechanism according to claim 12, in which:

the first cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate when fastened to the body panel. 14. A window regulator mechanism according to claim 13, in which:

the second cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate. 15. A window regulator mechanism according to claim 1, in which:

the first cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate when fastened to the body panel. 16. A window regulator mechanism according to claim 15, in which:

the second cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate. t t t III 

1. A window regulator mechanism adapted to lower or raise a window panel into or out of a window well between vehicle body panels, the window panel being vertically divided into separately movable ventilation and visibility sections, the window regulator mechanism comprising: a mounting plate secured to one of the body panels, a gear sector rotatably mounted on a pivot shaft journalled in the mounting plate, a first and a second regulator arm each swingable at one of its ends about a common pivot axis on the mounting plate, the other ends of the first and second regulator arms being coupled, respectively, to the ventilation section and the visibility section, a drag link pivotally connected to the gear sector for swinging movement in response to movement of the gear sector, a first and a second drive link each coupled at one of its ends to the drag link and at its other end to the first and second regulator arms, respectively, a first and a second cam plate positioned on the one body panel in predetermined relationship to the mounting plate, each cam plate having a cam slot therein, a cam follower carried on each of the drive links engaged with a cam slot in a respective cam plate, the cam slots being programmed so that movement of a follower therein controls the transmittal of movement of the gear sector through the drag link and drive links to the respective regulator arms, a predetermined degree of gear sector rotation in window panel lowering direction causing the first drive link, under control of its cam follower as the latter moves through a first section of tHe cam slot in the first cam plate, to drive the first regulator arm and thereby the ventilation section to a predetermined position in the window well as the cam follower on the second drive link moves along a first section of the cam slot in the second cam plate in which the second drive link is inoperative to drive the second regulator arm and thereby the visibility section in window panel lowering direction, and further gear sector rotation causing the second drive link, under control of its cam follower as the latter moves along a second section of the cam slot in the second cam plate, to drive the second regulator arm and thereby the visibility section in window panel lowering direction as the cam follower on the first drive link moves along a second section of the cam slot in the first cam plate without causing the first drive link to further drive the first regulator arm and thereby the ventilation section in window panel lowering direction, and drive pinion means for rotating the gear sector about its pivot axis.
 2. A window regulator mechanism according to claim 1, in which: the regulator arms are swingable about the pivot axis defined by the gear sector pivot shaft.
 3. A window regulator mechanism according to claim 2, in which: the second drive link during movement relative to the first section of its related cam slot restrains downward movement of the visibility section upon the direct application of downward force to the latter.
 4. A window regulator mechanism according to claim 3, in which: the drag link is pivotally connected directly to the gear sector.
 5. A window regulator mechanism according to claim 4, in which: the second regulator arm is fixed to the pivot shaft to cause the latter to rotate in the mounting plate, and counterbalance spring means coupled to the pivot shaft and mounting plate counterbalances the weight of the visibility section on the second regulator arm.
 6. A window regulator mechanism according to claim 5, in which: the first cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate when fastened to the body panel.
 7. A window regulator mechanism according to claim 6, in which: the second cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate.
 8. A window regulator mechanism according to claim 1, in which: the drag link is pivotally connected directly to the gear sector.
 9. A window regulator mechanism according to claim 8, in which: the second regulator arm is fixed to the pivot shaft to cause the latter to rotate in the mounting plate, and counterbalance spring means coupled to the pivot shaft and mounting plate counterbalances the weight of the visibility section on the second regulator arm.
 10. A window regulator mechanism according to claim 9, in which: the first cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate when fastened to the body panel.
 11. A window regulator mechanism according to claim 10, in which: the second cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate.
 12. A window regulator mechanism according to claim 1, in which: the second regulator arm is fixed to the pivot shaft to cause the latter to rotate in the mounting plate, and counterbalance spring means coupled to the pivot shaft and mounting plate counterbalances the weight of the visibility section on the second regulator arm.
 13. A window regulator mechanism according to claim 12, in which: the first cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate when fastened to the body panel.
 14. A window regulator mechaNism according to claim 13, in which: the second cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate.
 15. A window regulator mechanism according to claim 1, in which: the first cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate when fastened to the body panel.
 16. A window regulator mechanism according to claim 15, in which: the second cam plate is pivotally mounted at one end on the gear sector pivot shaft to provide for angular adjustment relative to the mounting plate. 